How can I execute commands on mysql using a php script?

<?  
    $sql = "select * from zen_admin";  
    $host = "localhost"; 
    $user = "username"; 
    $pass = "password"; 
    $db = "database";  
    $conn = mysql_connect($host, $user, $pass); 
    mysql_select_db($db, $conn);  
    echo "<pre>"; 
    $r = mysql_query($sql,$conn); 
    $results = mysql_fetch_array($r, MYSQL_ASSOC);  
    print_r($results);  
    mysql_free_result($r);  
    echo "</pre>";
?> 
 DONE.